Projection lithography machine is used for manufacturing large scale integrated circuit (LSI) and micro-electromechanical systems (MEMS). Projection lithography machine comprises an illumination system and a projection objective. The illumination system illuminates the mask with high uniformity, and a fine pattern on the mask is imaged onto photoresist on silicon wafer by the projection objective. The illumination system is mainly used for laser beam shaping, uniform illumination, changing the coherence factor, polarization control, and field control.
U.S. Pat. No. 7,187,430B2 discloses an illumination system which comprises a diffractive optical element, a zoom lens group, a conical lens group, a microlens array, a condenser lens group, a scanning slit, and an illumination lens group et al. The collimated beam is incident onto the diffractive optical element. The beam passes through the diffraction optical device, the zoom lens group, the conical mirror group and then forms a light intensity distribution on the microlens array surface (the light intensity distribution is called intensity mode in the projection lithography). The laser beam forms a rectangular spot with uniformity better than 99% by a microlens array and a condenser lens. The rectangular spot is projected on to the mask plane by the projection lens group. The scanning slit not only controls the size of the exposure field but also determines the intensity uniformity of exposure field. Therefore, the machining precision and speed precision of the scanning slit directly affect the performance of the projection lithography machine. Motion control components and dynamics analysis of the scanning slit are extremely complex, and it requires special isolation unit to avoid vibration from the scanning silt, which also increases the system complexity and cost.
U.S. Pat. No. 7,982,855B2 discloses an illuminator for microlithography device (i.e., an illumination system). The illuminator cuts angle spectrum to replace the existing slit scanning. The advantages are that it can not only reduce the scanning speed and scanning range but also eliminate the illumination lens group. However, it requires higher scanning speed and positional accuracy.